"Anjan Dave" <adave(at)vantage(dot)com> writes:
> Question is, does the 80MB buffer allocation correspond to ~87MB per
> postmaster instance? (with about 100 instances of postmaster, that will
> be about 100 x 80MB =3D 8GB??)
Most likely, top is counting some portion of the shared memory block
against each backend process. This behavior is platform-specific,
however, and you did not tell us what platform you're on.
> Interestingly, at one point, we vacuumed the database, and the size
> reported by 'df -k' on the pgsql slice dropped very
> significantly...guess, it had been using a lot of temp files?
"At one point"? If your setup doesn't include *routine* vacuuming,
you are going to have problems with file bloat. This isn't something
you can do just when you happen to remember it --- it needs to be driven
off a cron job or some such. Or use the contrib autovacuum daemon.
You want to vacuum often enough to keep the database size more or less
constant.
regards, tom lane